A sprinkler is known which has its own control valve for turning the sprinkler on and off. Such a sprinkler is often referred to as a "valve in head" sprinkler which means that the control valve for that sprinkler is built as part of the sprinkler head, i.e. that the valve is "in" the head. Valve in head sprinklers are typically larger sprinklers for watering larger areas. They are often used on golf courses or other large turf applications.
Some control valves in "valve in head" sprinklers are hydraulically actuated using a small bypass water flow to a pilot valve. The pilot valve water flow is typically dumped into the sprinkler bowl. This water can flood out of the bowl and onto the ground surrounding the sprinkler. This flooding can unduly soften and thus damage the turf surrounding the sprinkler.
Moreover, if water is left standing in a sprinkler bowl for an extended time, it can become laden with dirt and other debris. In extreme cases, this might impede the proper performance of the sprinkler. For example, it might prevent the sprinkler riser from properly popping up or down or might prevent the nozzle from rotating as it should. Accordingly, dumping the pilot valve water flow into the sprinkler bowl has various disadvantages.
Certain prior art sprinklers have attempted to solve this problem by NOT dumping the water flow from the pilot valve into the sprinkler bowl. These sprinklers use an extra return tube to carry the pilot valve water flow back into the main water flow inside the sprinkler body. Thus, the pilot valve water flow is merged back into the main water flow through the sprinkler body. Eventually, the pilot valve water flow is ejected through the sprinkler nozzles as part of the main water flow.
The approach detailed above is effective for preventing the pilot valve water flow from entering the sprinkler bowl. However, the pilot valve water flow is not the only water that can enter the sprinkler bowl. For example, water already standing on the ground or rain water can drain or flood into the sprinkler bowl. This is particularly true when the sprinkler is in a low area in the irrigation system. Preventing the pilot valve water flow from reaching the sprinkler bowl does nothing to remove any ground or rain water that might reach the sprinkler bowl.